Polyaxial bone anchor with polymer sleeve

ABSTRACT

A bone anchor assembly comprising a shank, receiver, pressure insert, sleeve and closure. The sleeve having a body constructed of deformable material and including a transfer of non deformable material molded into the body of the sleeve to transfer force around the body. The receiver having interior guides and the insert having guide followers that cooperate to align the insert in the receiver and prevent rotation of the insert in the receiver.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/731,064, filed Jun. 4, 2015, now U.S. Pat. No. 9,597,119, whichclaims the benefit of U.S. Provisional Application No. 62/007,616 filedJun. 4, 2014, each of which is incorporated by reference herein for allpurposes.

BACKGROUND OF THE INVENTION

Bone anchors are commonly used in implants to provide an anchored andstable platform for rods, cords and other structure utilized to connectvarious bones, especially vertebrae. Such implants replace missing bone,support damaged or diseased bone and otherwise support, replace orstrengthen the bones, especially the vertebrae of the spine. In certainsituations only two vertebrae are joined, whereas in other casesmultiple vertebrae are joined.

In general, the art of joining bones using basic system of metal bonescrews joined to metal rods is known and established, but does notprovide for improvements that give greater flexibility to both thesurgeon and the patient.

SUMMARY OF THE INVENTION

A spinal implant system includes bone anchors, which may be bone screws,or structures, such as a hook or the like, that join indirectly to thebone by being joined to a rod that is in turn joined to a bone anchor.The implant system includes at least one bone anchor having a receiverthat has a rod or cord receiving channel, a sleeve, and a closure. Whenthe bone anchor is a polyaxial bone screw, such an anchor also includesa threaded shank with an upper capture structure that is received in thereceiver and polyaxially rotates therewith during positioning. Theanchor preferably also includes a pressure insert located above theshank capture structure for locking the position of the shank when fullyassembled. Importantly, the sleeve in this embodiment is made of anon-metallic and flexible or deformable material except for a forcetransfer structure that is molded or otherwise formed into the sleeve.

An elongate member such as a flexible and tensionable cord is receivedthrough a bore in the sleeve. The sleeve is secured in the receiver byadvancement of the closure that applies downward force through thetransfer structure to the pressure insert which in turn transfers theforce to the capture structure of the shank, so as to abut the shankagainst an interior chamber wall of the receiver either directly orthrough a retainer to lock the shank in a selected angular positionrelative to the receiver.

In this manner the transfer structure transfers the force withoutdeforming or otherwise applying damaging force to the flexible sleeveand/or the elongate member.

The receiver includes a series of spaced guides that cooperate withguide receiving structure on the pressure insert to both properly alignthe insert relative to the receiver when loading the insert into thereceiver and to prevent rotation of the insert relative to a centralvertical axis of the receiver. The guides allow vertical sliding of theinsert relative to the receiver. The receiver and insert can be usedwith a rod and/or a sleeve, as shown herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded side elevational view of a bone anchor assembly inaccordance with the invention, including a shank, a retainer, a pressureinsert, a receiver, a sleeve, a closure, a pair of spacers with spacerinserts, and an elongate member.

FIG. 2 is a perspective view of the assembly of FIG. 1 fully assembled.

FIG. 3 is a cross sectional view of the assembly of FIG. 2, taken alongline 3-3 of FIG. 2.

FIG. 4 is an exploded view of a second configuration of a bone screwassembly similar to FIG. 1 with a different sleeve and a bumper/blockercombination.

FIG. 5 is a cross sectional view of the assembly shown in FIG. 4 bothassembled and vertically cross sectioned.

FIG. 6 is a top plan view of the shank.

FIG. 7 is a cross sectional view of the shank, taken along line 7-7 ofFIG. 6.

FIG. 8 is a side elevational view of the receiver.

FIG. 9 is a bottom plan view of the receiver.

FIG. 10 is a top plan view of the receiver.

FIG. 11 is a cross sectional view of the receiver, taken along line11-11 of FIG. 10.

FIG. 12 is a perspective view of the retainer.

FIG. 13 is a cross sectional view of the retainer taken across line13-13 of FIG. 12.

FIG. 14 is a perspective view of the pressure insert.

FIG. 15 is a bottom plan view of the pressure insert.

FIG. 16 is a side elevational view of the pressure insert.

FIG. 17 is a top plan view of the pressure insert.

FIG. 18 is a perspective view of the first sleeve of the embodiment ofFIG. 1.

FIG. 19 is a top plan view of the first sleeve.

FIG. 20 is a first side elevational view of a first end of the firstsleeve with the opposite side being a mirror image thereof.

FIG. 21 is a bottom plan view of the first sleeve.

FIG. 22 is a front elevational view of the first sleeve with the rearview being a mirror image thereof.

FIG. 23 is a perspective view of the second sleeve used in theembodiment of FIG. 3.

FIG. 24 is a top plan view of the second sleeve.

FIG. 25 is a first side elevational view of the second sleeve.

FIG. 26 is a second side elevational view of the second sleeve.

FIG. 27 is a bottom plan view of the second sleeve.

FIG. 28 is a front elevational view of the second sleeve.

FIG. 29 is a perspective view of a transfer structure utilized with boththe first and second sleeves.

FIG. 30 is a top plan view of the transfer.

FIG. 31 is a first side elevational view of the transfer structure withthe opposite side view being a mirror image thereof.

FIG. 32 is a front elevational view of the transfer with the rear viewbeing a mirror image thereof.

FIG. 33 is a bottom plan view of the transfer.

FIG. 34 is a perspective view of the sleeve.

FIG. 35 is a side elevational view of the sleeve.

FIG. 36 is a front elevational view of the sleeve.

The drawings constitute a part of this specification and includeexemplary embodiments of the present invention and illustrate variousobjects and features thereof.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT

As required, detailed embodiments of the present invention are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely exemplary of the invention, which may be embodied in variousforms. Therefore, specific structural and functional details disclosedherein are not to be interpreted as limiting, but merely as a basis forthe claims and as a representative basis for teaching one skilled in theart to variously employ the present invention in virtually anyappropriately detailed structure.

Illustrated in FIG. 1 is an exploded view of a spinal implant assemblygenerally indicated by the reference numeral 1. The assembly 1 includesa bone anchor 5 with a spacer 6 and a blocker 7.

The bone anchor 5 is illustrated as a bone screw, however, it isforeseen that the present invention may be utilized with various typesof anchors. The bone anchor 5 includes a shank 10, a retainer 11, apressure insert 12, a receiver 13, a first sleeve 14 and a closure 15.

The shank 10 has a capture or upper portion 17 and a lower portion 18.The upper portion 17 has a bulbous or partially spherically shaped head20 and is joined to the lower portion by a neck 21. The head 20 has anupper surface and a central tool engagement structure 23 that has lobes24 that are adapted to engage a driving tool (not shown) for implantingthe shank 10 into a vertebra of a patient. The upper surface 22 alsoincludes a plurality of concentric friction enhancing ribs 25.

The shank lower portion 18 is elongate and has an exterior thread 28adapted to thread into the vertebra of a patient. The shank 10 has acentral bore 29 providing cannulation for insertion over a guide wireduring implantation.

The receiver 13 is best seen in FIGS. 8 to 11. The receiver 13 has alower body 35 with a pair of upstanding and spaced arms 36 and 37forming a channel 38 therethrough for receiving a rod or a sleeve. Thechannel 38 has a lower surface 39 that is sized and shaped to be spacedfrom the bottom half of the elongate member 40, surrounded by thesleeve, or a rod.

The receiver 13 has an interior chamber 45 connecting with the exteriorof the receiver 13 through a lower aperture 46, as well as, upwardlyjoining with the channel 38. Near the lower end of the chamber 45 arelocated an upper groove 48 and a lower groove 49. The grooves 48 and 49are concentric, abutting and the upper groove 48 has a somewhat largerdiameter than the lower groove 49.

The receiver arms 36 and 37 have inwardly directed and facing sides 50that include helically wound guide and advancement structure 51 that areshown as reverse angle threads, but may be other types of threads andthe like, including V-threads, buttress threads, square threads,rectangular threads and flange forms.

The receiver 13 has a generally vertically aligned central axis A.Mounted in the chamber 45 at spaced locations from each other are fourguides 52. The guides 52 are located near the top of the chamber 45 andproject generally radially into the chamber 45 relative to the axis A.The guides 52 importantly interact with the insert 12 as discussedbelow.

Shown in FIGS. 12 and 13 is the retainer 11 that includes expandablering 53 with a gap 54. The retainer 12 is sized to snugly fit into thereceiver lower locking groove 49 while being expandable when alignedwith the upper expansion groove 48. During assembly, the ring 53 isplaced in the chamber 45 and the shank head 20 is pushed therethroughwhile the ring 53 is aligned with the upper groove 48 after which theshank 10 is lowered until the ring 53 is in the lower groove 49 andthereafter prevented from expanding, thus capturing the shank 10, butallowing the shank 10 to polyaxially rotate during positioning prior tolocking.

The insert 12 is best seen in FIGS. 14 to 17. The insert 12 has a lowerbody 55 with a pair of upstanding spaced arms 56 and 57 forming aU-shaped channel 58 therebetween which aligns with the receiver channel38. The insert 12 has a bore 59 that aligns with the axis A. At the topof each arm 56 and 57 is a pressure transfer surface 65 each of whichhas an upward extending and centrally located nub 66. Circumferentiallylocated at equally spaced locations about the body 55 and extending intothe arms 56 and 57 are four guide mating structures 68. Each structureincludes a pair of vertically aligned walls 70 and 71 that merge at acentral vertex 72 to form V-shaped slots that are sized and shaped toreceive the guides 52. While V-shaped grooves are illustrated, it isforeseen that the mating structures 68 may have other vertically oraxially aligned shapes including slots, indentations, or the like. Inthis manner, the guides 52 allow the insert 12 to easily slide upward inproper position relative to the receiver while preventing the insert 12from rotating about the axis A relative to the receiver 13. Located atthe bottom of the walls 70 and 71 is a stop 75 that limits the elevationof the insert 12 in the receiver 13 during assembly. The illustratedinsert 12 is bottom loaded through the lower receiver aperture 46;however, it is foreseen that the insert 12 may also be top loadedthrough the chamber 45 in which case the stop 75 would not be utilized.

It is foreseen that the guide mating structure 68 may include corners,shoulders or other features that allow the insert 12 to slidevertically, but that prevent the insert 12 from rotating axiallyrelative to the receiver 13. It is noted that the guide receivingstructure 68 and guide 52 cooperation also allows the insert 12 to beeasily aligned with and guided into proper position in the receiver 13during assembly.

Shown in FIGS. 18 to 22 is the first sleeve 14. The sleeve 14 includes abody 80 sized and shaped to fit in the receiver channel 38 between thearms 36 and 37. Extending laterally from the body 80 are a pair of sideelements or extensions 81 and 82. As will be noted later, someembodiments have only a single extension. The extensions 81 and 82 matewith the spacers 6. The sleeve 14 has a bore 83 that extends from sideto side and is sized and shaped to slidingly receive the elongate member40. Each extension 81 and 82 includes a vertically aligned abutment orstop surface 85 that is located near the bone anchor 5 in use.

Located on the top side and in the middle of the sleeve 14 is a transferreceiving structure 86 that mates with and receives a transfer 87.

The sleeve 14 is constructed of a deformable material that is suited forreceiving a pliable, flexible and often elastic elongate member 40without damaging the member 40 as it slides or moves therein. The sleeve14 is preferably made of a material such as PEEK (polyether etherketone), ultra high density polyethylene, various types of polyurethane,especially calcium carbonate filed polyurethane, i.e. PCU, or graphitefiled polyurethane, and the like. Such materials while initially beingat least somewhat solid, will deform over time in this service due tothe pressure exerted thereon by the closure 15. Because of this thematerials will creep, or the like, and may cause the strength of theimplant 1 to weaken.

The transfer 87 is metallic in nature and is more rigid than theremainder of the sleeve 14, that is, the transfer 87 is designed to bemore rigid and less prone to creep than the remainder of the sleeve 14.Preferably, the transfer 87 is made of metal, such as stainless steel,various metal alloys, including such often called cobalt-chrome andcobalt-chrome-molybdenum, titanium, or various titanium alloys and otherinplantable metals. The transfer 87 is molded into the sleeve 14 andbecomes an integral part of the sleeve 14.

Shown in FIGS. 24 to 28 is a second sleeve 90 that is the same as sleeve14 except that the sleeve 90 has only one extension 91. The sleeve 90also includes a molded transfer 87. The purpose of the sleeves 14 and 90will be discussed below.

The transfer 87 that is seen best in FIGS. 29 to 33 has an upper body 95with spaced depending legs 96 and 96 forming a saddle shaped structure98 that is sized and shaped to mate with the top of the sleeves 14 and90 when molded therein, but also bridge over the elongate member 40during use. Each of the legs 96 and 97 have lower surfaces 101 that aresized, shaped and positioned to engage and press on the top surfaces ofthe insert arm top surfaces 65 so as to transfer force exerted by theclosure 15, as discussed below, to the pressure insert 12, which forceis then transferred to the shank 10 for locking the position of theshank 10 relative to receiver 13. In this manner, the force associatedwith locking the shank 10 is neither transferred to the elongate member40 or to the sleeves 14 and 90. Each transfer leg lower surface 101 hasan indent 103 that aligns with and snugly receives the nubs 66 on thetop of the insert arms 56 and 57 for stability and to resist torsion.Opposed projections 104 extend laterally from each side of the transfer87 to be imbedded in the sleeves 14 and 90 to resist torquing of thetransfer 87 relative to the sleeves 14 and 90 during tightening of theclosure 15.

The transfer 87 has a vertically and axially aligned passthrough bore105 to allow passage of various parts of the overall implant assembly 1in various configurations.

The closure 15 has a cylindrical shaped body 108 with helically woundguide and mating structure 109 that aligns with and rotates into theguide and advancement structures 51 on the receiver arms 36 and 37. Aconventional axially aligned drive 110 is utilized to rotate the closure15. The closure can have a break off head and be configured to penetratethe elongate member such as a cord.

One of the spacers 6 used in the assembly 1 is illustrated in FIGS. 34to 36. The spacer 6 includes a body 108 with an elongate passthroughbore 109 sized to slidingly receive the elongate member 40. The spacer 6includes a relief groove 110 partially around one end and radiallypositioned with respect to the bore 109 to allow greater flexibilitythereat. Opposite ends 111 and 112 of the spacer 6 are sized, shaped andconfigured to mate with and overlap the sleeve extensions 81 and 82.Each spacer 6 also includes an axial insert 113.

Shown in FIGS. 1 to 3 is a first configuration 120 of the assembly 1.The configuration 120 is utilized when the bone anchor 5 is positionedbetween two other bone anchors (not shown). In such a configuration theelongate members will extend between all of the joined bone anchors 5and spacers 6 will be between each adjacent pair of bone anchors 5. Forthe configuration 120, the sleeve 14 is utilized.

Shown in FIGS. 4 and 5 is a second configuration 121. The configuration121 is utilized where the bone anchor 5 is the last in a series of boneanchors 5, here extending to the right. In the configuration 121, abumper 122 and a blocker 7 are used to secure the elongate member 40, inthis embodiment a tensionable cord. The bumper 121 is resilient andcompressible and surrounds the elongate member 40 during use whileabutting against the bone anchor 5. The blocker 7 receives the elongatemember 40 and captures the member 40 therein by compression of a breakoff set screw 124 configured to penetrate and lock the cord.

In configuration 121 shown in FIG. 4, the second sleeve 90 is utilizedand normally a spacer 6 (not shown). Other configurations of theassembly 1 are foreseen.

It is to be understood that while certain forms of the present inventionhave been illustrated and described herein, it is not to be limited tothe specific forms or arrangement of parts described and shown.

What is claimed and desired to be secured by Letters Patent is asfollows:
 1. A spinal implant sleeve positionable in a channel of areceiver of a bone anchor assembly, the bone anchor assembly including apressure insert and a bone anchor having a head end opposite an anchorend, with the pressure insert also being positionable in the receiverchannel above the head end of the bone anchor, the sleeve comprising: asleeve body constructed of a non-rigid deformable material and having aclosed bore extending therethrough for receiving a tensioned cord; and atransfer structure constructed of a rigid non-deformable material,wherein the transfer structure is incorporated into the sleeve body toreceive a force from above the sleeve and transfer the force around thesleeve body of the sleeve and onto the pressure insert positioned withinthe receiver channel above the head end of the bone anchor.
 2. Thesleeve of claim 1, further comprising projections extending from thetransfer structure to resist torque of the transfer structure relativeto the sleeve body.
 3. The sleeve of claim 2, wherein the projectionsextend from the transfer structure into the sleeve body.
 4. The sleeveof claim 1, wherein the transfer structure is constructed of a patientimplantable metal.
 5. The sleeve of claim 4, wherein the transferstructure is constructed of a cobalt chrome alloy.
 6. The sleeve ofclaim 4, wherein the transfer structure is constructed of a metalselected from titanium and titanium alloys.
 7. The sleeve of claim 1,wherein the sleeve body is constructed of a thermoplastic polymer. 8.The sleeve of claim 1, wherein the sleeve body is constructed of apolyurethane material.
 9. The sleeve of claim 1, wherein the sleeve bodyis constructed of PEEK.
 10. The sleeve of claim 1, wherein the sleevebody is constructed of ultra-high molecular weight polyethylene.
 11. Apivotal bone anchor assembly for securing an elongate rod to a bone, thebone anchor assembly comprising: a receiver having a channel adapted toreceive one of an elongate member and a tensioned cord; a pressureinsert positioned in the receiver and having upward extending arms andeach of the arms having upper surfaces; a sleeve positioned in thechannel above the pressure insert and in combination with the one of anelongated member and a tensioned cord, the sleeve comprising: a sleevebody constructed of a deformable material and having a closed boreextending therethrough for receiving the elongate member or tensionedcord; and a transfer structure constructed of a rigid material andhaving depending legs with lower surfaces that align and mate with theupper surfaces on the pressure insert arms in an overlappingrelationship; and a closure positioned in the receiver above the sleeve,wherein the transfer structure is incorporated into the sleeve body andconfigured to receive a force from the closure and transfer the forcearound the sleeve body to the pressure insert without transferringpressure directly through the deformable material of the sleeve body.12. The bone anchor assembly of claim 11, further comprising projectionsextending from the transfer structure to resist torque of the transferstructure relative to the sleeve body.
 13. The bone anchor assembly ofclaim 12, wherein the projections extend from the transfer structureinto the sleeve body.
 14. The bone anchor assembly of claim 11, whereinthe transfer structure is constructed of a metal alloy selected fromcobalt chrome and titanium alloys.
 15. The bone anchor assembly of claim11, wherein the deformable material is a polymer selected from the groupconsisting of PEEK, PCU, graphite-filled polyurethane, and ultra highmolecular weight polyethylene.
 16. The bone anchor assembly of claim 11,further comprising an implantable shank received in the receiver andreceiving downward force from the insert.
 17. The bone anchor assemblyof claim 11, further comprising a retainer positioned within thereceiver below the pressure insert and configured to capture and securea head of an implantable shank within an interior chamber of thereceiver.